This project is to develop an ultra-miniature catheter-tip pressure transducer to be mounted in a catheter suitable for use in transgenic mice weighing twenty grams or less. The initial prototype transducer will be 1.OF (0.33 mm OD) in diameter, which has been modeled under the Phase I project. A smaller diameter transducer will be developed in this Phase II effort. The sensor will have a high frequency response sufficient for accurate reproduction of transgenic mouse blood pressure waveforms, at heart rates of up to 1,000 beats per minute with pressure change rates of up to 20,000 mmHg per second. The high-fidelity ultra-miniature catheter will enable researchers to investigate mouse hemodynamics throughout the cardiovascular system, including renal arteries. A femoral approach will now be possible, similar to the procedure used in human cardiac catheterizations. Since many forms of heart disease are caused by or affected by genetic factors, the transgenic mouse is the research animal of choice. Investigations of genes active in juvenile mice but not in adult mice will now be possible with access to smaller arteries. A more complete description of the effect of a single gene on the cardiovascular system would further the search for cures of these diseases, the leading cause of death in America.